Cream butter, sugar, egg yolk and vanilla until light and fluffy. Stir in flour until just combined. Refrigerate 1 hour. Preheat oven to 350~F. Using hands, roll dough into 1" balls. Dip in egg white, then roll in pecans. Place on ungreased cookie sheet and bake 5 minutes. Remove from oven and with the end of a wooden spoon, make a depression in the center of each cookie. Return to the oven and bake another 8-10 min. until a delicate brown. remove to a wire rack to cool. Fill indention with a dot of powdered sugar frosting. While still warm, place a rounded edge of a maraschino cherry in center. Jelly may also be used in the centers. Margaret Garland DFYX18A